Joint bushings for track joint assemblies

ABSTRACT

A thrust ring comprises a body including a cylindrical outer surface, a cylindrical inner surface, defining a central axis, an axial direction, a circumferential direction, a first axial end, a second axial end, and at least one recess on the first axial end, and at least one protrusion extending from the cylindrical inner surface toward the central axis.

CROSS-REFERENCE TO RELATED APPLICATION

This continuation application claims the benefit of U.S. patentapplication Ser. No. 14/461,328 filed on Aug. 15, 2014, which claims thebenefit of U.S. Provisional Patent Application No. 61/871,505, filed onAug. 29, 2013, both of which are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates generally to track assemblies and, moreparticularly, to track joint assemblies for joining links of the trackassemblies.

BACKGROUND

Many earth-working machines, such as, for example, loaders, tractors,and excavators, include tracked undercarriages to facilitate movement ofthe machines over ground surfaces. Such undercarriages include drivesprockets that rotate track assemblies about one or more idlers or otherguiding components to propel the machines over the ground surfaces. Eachtrack assembly includes a pair of parallel chains, each made up of aseries of links, joined to each other by pins and/or bushings (thecombination of which is sometimes referred to as a cartridge assembly).Due to extreme wear from abrasion and impacts experienced during use,undercarriage maintenance costs often constitute more than one quarterof the total costs associated with operating the earth-working machines.

FIG. 1 provides an example of a prior art cartridge assembly 10 forcoupling links, which is disclosed by U.S. Patent ApplicationPublication No. 2012/0267947 by Johannsen et al. As shown, cartridgeassembly 10 includes a pin 12 accommodated within an inner bushing 14,which is, in turn, accommodated within an outer bushing 16. End portions17 a, 17 b of inner bushing 14 are surrounded by inserts 19 a, 19 b, andend portions 21 a, 21 b of pin 12 are surrounded by collars 23 a, 23 b.Pin 12 has a lubricant channel 25, which serves as a reservoir forlubricant and delivers lubricant to a gap between pin 12 and innerbushing 14, and to a gap between inner bushing 14 and outer bushing 16.The lubricant is retained by seals 27 a, 27 b positioned between outerbushing 16 and inserts 19 a, 19 b, and by seals 29 a, 29 b positionedbetween inserts 19 a, 19 b and collars 23 a, 23 b.

Cartridge assembly 10 may provide certain benefits that are particularlyimportant for some applications. However, it may have certain drawbacks.For example, manufacturing pin 12 to include channel 25 may becomplicated and costly. As another example, manufacturing links largeenough to accommodate inserts 19 a, 19 b and collars 23 a, 23 b (asopposed to just pin 12 and inner bushing 14) may require an excessiveamount of material. The disclosed embodiments may help solve theseproblems.

SUMMARY

A thrust ring according to an embodiment of the present disclosurecomprises a body including a cylindrical outer surface, a cylindricalinner surface, defining a central axis, an axial direction, acircumferential direction, a first axial end, a second axial end, and atleast one recess on the first axial end, and at least one protrusionextending from the cylindrical inner surface toward the central axis.

A track joint assembly according to an embodiment of the presentdisclosure comprises a first link defining a pin bore, a lubricatingfluid cavity bore in communication with the pin bore, and an openingextending from the exterior of the link to the lubricating fluid cavity;and a thrust ring disposed in the lubricating fluid cavity, the thrustring comprising a body including a cylindrical outer surface, acylindrical inner surface, defining a central axis, an axial direction,a circumferential direction, a first axial end, a second axial end, andat least one recess on the second axial end positioned adjacent theopening of the link being in fluid communication therewith, and at leastone protrusion extending from the cylindrical inner surface toward thecentral axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a prior art cartridge assembly;

FIG. 2 is a perspective view of a track assembly according to thepresent disclosure;

FIG. 3 is a cutaway view of a track joint assembly of the track assemblyof FIG. 2;

FIG. 4 is a cross-section of the track joint assembly of FIG. 3;

FIG. 5 is an enlarged view of a portion of FIG. 4;

FIG. 6 is another enlarged view of a portion of FIG. 4;

FIG. 7 is a perspective view of a thrust ring of the track jointassembly of FIG. 3;

FIG. 8 is a side view of the thrust ring of FIG. 7;

FIG. 9 is a cross-section of the thrust ring of FIG. 7;

FIG. 10 is a cross-section of another track joint assembly according tothe present disclosure; and

FIG. 11 is a cross-section of yet another track joint assembly accordingto the present disclosure.

DETAILED DESCRIPTION

FIG. 2 illustrates an exemplary track assembly 100 for a track-typemachine. For example, the track-type machine may be a loader, a tractor,an excavator, a tank, or another mobile machine having track-typetraction devices. When operated, a drive sprocket of the track-typemachine (not shown) may rotate track assembly 100 about one or moreidlers or other guiding components (not shown) to facilitate movement ofthe track-type machine.

Track assembly 100 may include a series of links 110 a joined to eachother and to a series of links 110 b by laterally disposed pins 120. Asshown, links 110 a and 110 b may be offset links. That is, they may haveinwardly offset ends 140 a, 140 b and outwardly offset ends 150 a, 150b. An inwardly offset end 140 a, 140 b of each link 110 a, 110 b may bejoined to an outwardly offset end 150 a, 150 b of each adjacent link 110a, 110 b. In addition, an inwardly offset end 140 a of each link 110 amay be joined to an inwardly offset end 140 b of an opposing link 110 b,and an outwardly offset end 150 a of each link 110 a may be joined to anoutwardly offset end 150 b of an opposing link 110 b. It should beunderstood, however, that links 110 a and 110 b need not be offsetlinks. Rather, in some embodiments, links 110 a and 110 b may be innerlinks and outer links. In such embodiments, both ends of each opposingpair of inner links would be sandwiched between ends of opposing outerlinks, as is known in the art.

Referring to FIGS. 3 and 4, an individual track joint assembly 155 oftrack assembly 100 may include two links 110 a joined to two links 110b. As shown, inwardly offset ends 140 a, 140 b of links 110 a, 110 b maybe secured to a joint bushing 157, which may be at least partiallypositioned within bushing bores 160 a, 160 b of offset ends 140 a, 140b. Similarly, outwardly offset ends 150 a, 150 b of links 110 a, 110 bmay be secured to a pin 120, which may be at least partially positionedwithin pin bores 170 a, 170 b of offset ends 150 a, 150 b. For example,the securing may be by way of press-fits. Specifically, bushing 157 maybe press-fit into bushing bores 160 a, 160 b, and pin 120 may bepress-fit into pin bores 170 a, 170 b. Alternatively, the securing maybe by way of welds, snap rings, or other mechanisms known in the art.

As shown, bushing 157 may be positioned coaxially around pin 120, andmay rotate relative to pin 120, allowing inwardly offset ends 140 a, 140b to pivot relative to outwardly offset ends 150 a, 150 b as trackassembly 100 rotates. In order to facilitate such rotation, one or bothof bushing 157 and pin 120 may be coated with diamond like carbon orelectroless nickel, or may be carburized, nitrided, or polished toreduce friction between bushing 157 and pin 120. Alternatively oradditionally, a lubricating fluid may be situated between bushing 157and pin 120.

The lubricating fluid may be added through openings 180 a, 180 b inlinks 110 a, 110 b, (extending axially from the exterior of the link 110a, 110 b and disposed radially above the pin bore 170 a, 170 b and beingin fluid communication with the lubricating fluid cavity 190) and may becontained in a lubricating fluid cavity 190 at least partially definedby a generally cylindrical inner surface 200 of inner bushing 157 and agenerally cylindrical outer surface 210 of pin 120 facing surface 200.Unlike the prior art cartridge assembly discussed above, lubricatingfluid cavity 190 may not extend into an interior cavity of pin 120, aspin 120 may be solid. Since pin 120 may not contain lubricating fluid,lubricating fluid cavity 190 may extend into and be at least partiallydefined by one or more recesses in surface 200 or surface 210.Alternatively or additionally, lubricating fluid cavity 190 may extendinto and be at least partially defined by thrust rings 220 a, 220 bpositioned at axial ends 230 a, 230 b of bushing 157. Thrust rings 220a, 220 b may transmit axial load between adjacent links 110 a, 110 b,and may limit axial load on seal assemblies 240 a, 240 b, which may bepositioned radially outward of thrust rings 220 a, 220 b and formhermetic seals between adjacent links 110 a, 110 b to retain thelubricating fluid in lubricating fluid cavity 190. More specifically,the thrust rings 220 a, 220 b are disposed in the lubricating fluidcavity 190 and the recess 530 (best seen in FIGS. 7 thru 9) on thesecond axial end 520-1 may be positioned adjacent the opening 180 a, 180b of the link 110 a, 110 b, allowing fluid communication therewith. Atleast one protrusion 540 is configured to abut or nearly contact the pin120 for transmitting radial loads and keeping the thrust ring 220 a, 220b centered about the pin 120. The protrusion 540 may be offset axiallytoward the second axial end 520-1.

Still referring to FIGS. 3 and 4, in some embodiments, track jointassembly 155 may also include an outer bushing 250, which may bepositioned coaxially around bushing 157 (making bushing 157 an innerbushing) to engage a drive sprocket (not shown) that rotates trackassembly 100. Outer bushing 250 may rotate relative to inner bushing 157when it engages the drive sprocket, reducing wear on outer bushing 250caused by sliding motion between outer bushing 250 and the drivesprocket. Such rotation may be facilitated by coating one or both ofouter bushing 250 and inner bushing 157 with diamond like carbon orelectroless nickel, or by carburizing, nitriding, or polishing one orboth of outer bushing 250 and inner bushing 157 to reduce frictionbetween outer bushing 250 and inner bushing 157. Alternatively oradditionally, lubricating fluid may be situated between outer bushing250 and inner bushing 157. This lubricating fluid may be the same as ordifferent from the lubricating fluid situated between inner bushing 157and pin 120.

The lubricating fluid may be added during assembly of track jointassembly 155, and may be contained in a lubricating fluid cavity 260 atleast partially defined by a generally cylindrical inner surface 270 ofouter bushing 250 and a generally cylindrical outer surface 280 of innerbushing 157 facing surface 270. Lubricating fluid cavity 260 may beisolated from lubricating fluid cavity 190 so that a leak in lubricatingfluid cavity 260 does not impact lubricating fluid cavity 190 (and viceversa). Lubricating fluid cavity 260 may extend into and be at leastpartially defined by one or more recesses in surface 270 or surface 280.Alternatively or additionally, lubricating fluid cavity 260 may extendinto and be at least partially defined by thrust rings 290 a, 290 b,which may be disposed in bushing bores 160 a, 160 b, and which may bepositioned at axial ends 300 a, 300 b of outer bushing 250 and coaxiallyaround inner bushing 157. Thrust rings 290 a, 290 b may limit axial loadon seal assemblies 310 a, 310 b, which may form hermetic seals betweenouter bushing 250 and links 110 a, 110 b to retain the lubricating fluidin lubricating fluid cavity 260.

As shown in FIG. 5 and discussed above, bushing 157 may be press-fitinto bushing bores 160 a, 160 b. In particular, axial end portions 320a, 320 b of bushing 157 may be disposed in and press-fit into outerportions 330 a, 330 b of bushing bores 160 a, 160 b. Additionally, axialend-adjacent portions 340 a, 340 b of bushing 157 may be disposed in andpress-fit into central portions 350 a, 350 b of bushing bores 160 a, 160b. Thus, axial end portions 320 a, 320 b may contact outer portions 330a, 330 b, and axial end-adjacent portions 340 a, 340 b may contactcentral portions 350 a, 350 b. In some embodiments, outer diameters 360a, 360 b of end-adjacent portions 340 a, 340 b may be larger than outerdiameters 370 a, 370 b of end portions 320 a, 320 b. Accordingly, outerportions 330 a, 330 b may have different diameters than central portions350 a, 350 b to account for the differences between diameters 360 a, 360b and 370 a, 370 b. In other embodiments, however, outer diameters 360a, 360 b of end-adjacent portions 340 a, 340 b may be the same as outerdiameters 370 a, 370 b of end portions 320 a, 320 b, in which case outerportions 330 a, 330 b might have the same diameters as central portions350 a, 350 b.

Referring again to FIG. 5, inner surface 200 of bushing 157 may includea generally cylindrical inner surface 380 defining a bore 390. Pin 120may be positioned at least partially within bore 390 and its motion maythus be constrained by surface 380. Accordingly, surface 380 may be abearing surface. As shown, inner surface 380 may include threevalley-shaped recesses 400, each extending into and along acircumference of bushing 157, and a sum of lengths 410 of recesses 400,in an axial direction of bushing 157, may be approximately 27% of alength 420 of surface 380. It should be understood, however, that innersurface 380 may include a different number of recesses or differentlysized recesses. For example, inner surface 380 may include between oneand twenty recesses 400, and the sum of lengths 410 may be betweenapproximately 5% and approximately 75% of length 420. It iscontemplated, however, that, by using a plurality of recesses 400 (asopposed to a single larger recess 400), the structural integrity ofbushing 157 may be maintained. It should also be understood that innersurface 380 may include differently positioned or shaped recesses. Forexample, inner surface 380 may include valley-shaped recesses extendingalong the axial direction of bushing 157. Alternatively, inner surface380 may include helical recesses extending along both circumferentialand axial directions of bushing 157.

Outer surface 280 of bushing 157 may include a generally cylindricalouter surface 430, which may constrain motion of outer bushing 250.Thus, surface 430 may be a bearing surface. As shown, outer surface 430may include a different number of recesses than inner surface 380, andits recesses may be offset, in the axial direction of bushing 157,relative to those of inner surface 380 in order to avoid compromisingbushing 157's structural integrity. Specifically, outer surface 430 mayinclude four valley-shaped recesses 440, each extending into and along acircumference of bushing 157, and a sum of lengths 450 of recesses 440,in the axial direction of bushing 157, may be approximately 37% of alength 460 of surface 430. It should be understood, however, that outersurface 430 may include a different number of recesses or differentlysized recesses. For example, outer surface 430 may include between oneand twenty recesses 440, and the sum of lengths 450 may be betweenapproximately 7% and approximately 38% of length 460. It iscontemplated, however, that, by using a plurality of recesses 440 (asopposed to a single larger recess 440), the structural integrity ofbushing 157 may be maintained. It should also be understood that outersurface 430 may include differently positioned or shaped recesses. Forexample, outer surface 430 may include valley-shaped recesses extendingalong the axial direction of bushing 157. Alternatively, outer surface430 may include helical recesses extending along both circumferentialand axial directions of bushing 157. In yet another alternative, outersurface 430 may include recesses that are aligned with (as opposed tooffset relative to) those of inner surface 380.

As shown in FIG. 6 and discussed above, thrust ring 220 a may bepositioned at axial end 230 a of bushing 157. Thrust ring 220 a mayinclude a generally cylindrical outer surface 465, which may supportseal assembly 240 a. In addition, thrust ring 220 a may include agenerally cylindrical inner surface 470, which may at least partiallydefine lubricating fluid cavity 190. As shown, an outer diameter 480 ofouter surface 465 (and thus thrust ring 220 a) may be larger than outerdiameter 370 a of axial end portion 320 a of inner bushing 157.Specifically, outer diameter 480 may be approximately 1.16 times outerdiameter 370 a. Alternatively, outer diameter 480 may be another size.For example, outer diameter 480 may be between approximately 1.1 andapproximately 2.0 times outer diameter 370 a. Also, the thrust ring 220a, 220 b may include a body having a generally cylindrical configurationdefining a central axis, an axial direction, and a circumferentialdirection.

Thrust ring 220 a's larger diameter may ensure that seal assembly 240 acontacts only links 110 a, not bushing 157. Specifically, seal assembly240 a may contact a sealing portion 485 of link 110 a at a seal-linkinterface 490. As shown, an outer diameter 500 of seal-link interface490 may be approximately 1.20 times outer diameter 370 a of axial endportion 320 a of inner bushing 157. Alternatively, outer diameter 500may be another size. For example, outer diameter 500 may be betweenapproximately 1.05 and approximately 2.5 times outer diameter 370 a.

Sealing portion 485 may include a sealing surface 505 of inwardly offsetend 140 a of link 110 a that faces outwardly offset end 150 a ofadjacent link 110 a. It may be annular and surround axial end 230 a ofaxial end portion 320 a, and may include a different material from otherportions of link 110 a. That is, it may have different materialproperties from other portions of link 110 a. The different material mayhave a different wear resistance than material of the other portions,and may better resist wear and corrosion resulting from sealing portion485's contact with seal assembly 240 a. For example, the differentmaterial may be an electroless nickel coating, a nitride coating, or acarborized coating. In some embodiments, the different material may be awasher 510 attached to link 110 a. For example, washer 510 may bepress-fit into another portion of link 110 a, welded to the otherportion, fastened to the other portion with an adhesive, or held in theother portion by an annular biasing member positioned at an innerdiameter or an outer diameter of washer 510. In other embodiments, thedifferent material may be clad (e.g., laser clad) to the material of theother portion of link 110 a. Alternatively, the different material maybe a laser hardened or a thermal sprayed material. In yet anotheralternative, the different material may be a thin film coating of, forexample, chromium nitride, amorphous diamondlike carbon, or tetrahedralamorphous carbon.

Referring to FIGS. 7-9, thrust ring 220 a may include axial ends 520-1and 520-2 (i.e. first axial end 520-1 and second axial end 520-2)connecting outer surface 465 of thrust ring 220 a to inner surface 470of thrust ring 220 a. As shown, each of axial ends 520-1 and 520-2 mayinclude two recesses 530, which may extend from outer surface 465 toinner surface 470 to facilitate lubricating fluid flow between anexterior of thrust ring 220 a and an interior of thrust ring 220 a.Alternatively, axial ends 520-1 and 520-2 may include another number ofrecesses. For example, in some embodiments, axial end 520-1 may includea different number of recesses than axial end 520-2. In someembodiments, there is at least one recess 530 on the first axial end520-1. In many embodiments, there is also at least one recess 530 on thesecond axial end 520-2. In still further embodiments, there are tworecesses 530 on the first axial end 520-1 that are disposeddiametrically opposite each other on the first axial end 520-1.Similarly, there may be two recesses 530 on the second end 520-2 thatare disposed diametrically opposite each other on the second end 520-2.In such a case, the two recesses 530 on the second axial end 520-2 maybe out of phase circumferentially with the two recesses 530 on the firstaxial end 520-1 by ninety degrees.

As shown in FIGS. 7-9, inner surface 470 of thrust ring 220 a mayinclude three protrusions 540, all extending along a circumference ofthrust ring 220 a and toward a central axis of thrust ring 220 a.Protrusions 540 may have approximately rectangular cross-sections 545,and may be offset, in an axial direction of thrust ring 220 a, from anaxial center of thrust ring 220 a, as best shown in FIG. 9. Someembodiments, however, may include different configurations ofprotrusions. For example, some embodiments may have only one protrusion,which may or may not extend along an entire circumference of thrust ring220 a. Other embodiments may have a plurality of protrusions, but suchprotrusions may be shaped or positioned differently than protrusions540. For example, instead of having approximately rectangularcross-sections, they may have approximately U-shaped or V-shapedprotrusions, and they may or may not be offset from the center of thrustring 220 a. In some embodiments, the three protrusions 540 are spacedcircumferentially from each other evenly.

FIG. 10 illustrates another embodiment of a track joint assembly 155′including a different bushing configuration. Instead of having innerbushing 157 and outer bushing 250, track joint assembly 155′ may includeonly a single bushing 157′. Otherwise, track joint assembly 155′ may beidentical to track joint assembly 155.

Bushing 157′ may be similar to bushing 157. Accordingly, only the waysin which bushing 157′ differs from bushing 157 will be described.Bushing 157′ may include a middle portion 570′ between axialend-adjacent portions 340 a′, 340 b′. Thus, middle portion 570′ may beseparated from axial end portions 320 a′, 320 b′ by axial end-adjacentportions 340 a′, 340 b′. Middle portion 570′ may have an outer diameter580′ that is larger than outer diameters 360 a′, 360 b′ of end-adjacentportions 340 a′, 340 b′ to maximize the amount of wear that middleportion 570′ may sustain as a result of engagement with the drivesprocket. For example, outer diameter 580′ may be approximately 1.49times outer diameters 360 a′, 360 b′. It should be understood, however,that outer diameter 580′ may be another size. For example, outerdiameter 580′ may be between approximately 1.25 and approximately 2.00times outer diameters 360 a′, 360 b′. In some embodiments, middleportion 570′ may be positioned at least partially within inner portions590 a′, 590b′ of bushing bores 160 a′, 160 b′. In other embodiments,middle portion 570′ may not be positioned at least partially withininner portions 590 a′, 590 b′.

FIG. 11 illustrates yet another embodiment of track joint assembly 155″including different bushing and link configurations. Like track jointassembly 155′, instead of having inner bushing 157 and outer bushing250, track joint assembly 155″ may include only a single bushing 157″.Additionally, instead of having links 110 a, 110 b, track joint assembly155″ may include links 110 a″ and 110 b″. Bushing 157″ may be similar tobushing 157′, and links 110 a″, 110 b″ may be similar to links 110 a′,110 b′ (and thus links 110 a, 110 b). Links 110 a″, 110 b″ may differfrom links 110 a′, 110 b′ only in that they include bushing bores 160a″, 160 b″ having only two portions (outer portions 330 a″, 330 b″ andcentral portions 350 a″, 350 b″) instead of three portions (outerportions 330 a′, 330 b′, central portions 350 a′, 350 b′, and innerportions 590 a′, 590b′). And bushing 157″ may differ from bushing 157′only in that middle portion 570″ may not be positioned at leastpartially within inner portions of bushing bores 160 a″, 160 b″.Otherwise, track joint assembly 155″ may be identical to track jointassemblies 155 and 155′.

The components of track joint assemblies 155, 155′, 155″ may beconstructed of various materials. In some embodiments, links 110 a, 110b, 110 a′, 110 b′, 110 a″, 110 b″; bushings 157, 157′, 157″; bushings250; thrust rings 220 a, 220 b; and thrust rings 290 a, 290 b may beconstructed of metal. For example, each of these components may beconstructed of a ferrous metal, such as steel or iron.

The configuration of track joint assemblies 155, 155′, 155″ is notlimited to the configurations discussed above and shown in the drawings.For example, outer surface 210 of pin 120 may include recesses insteadof inner surface 200 of bushing 157. Such recesses may be similar torecesses 440 in outer surface 280 of bushing 157. As another example,inner surface 270 of outer bushing 250 may include recesses instead ofouter surface 280 of bushing 157. Such recesses may be similar torecesses 400 in inner surface 200 of bushing 157.

INDUSTRIAL APPLICABILITY

The disclosed track joint assemblies may be applicable to track-typemachines, such as, for example, loaders, tractors, excavators, andtanks, and may facilitate movement of the machines. The disclosed trackjoint assemblies may have various advantages over prior art track jointassemblies. For example, the disclosed track joint assemblies may bestronger and more durable than prior art track joint assemblies. Inaddition, manufacturing the disclosed track joint assemblies may costless than manufacturing prior art track joint assemblies, and mayrequire less material than manufacturing prior art track jointassemblies. Specific advantages of the disclosed track joint assemblieswill now be described.

Track joint assembly 155 may include direct connections between links110 a, 110 b that strengthen and improve the durability of track jointassembly 155. Specifically, inwardly offset ends 140 a, 140 b of links110 a, 110 b may be directly connected by being secured to bushing 157.Likewise, outwardly offset ends 150 a, 150 b of links 110 a, 110 b maybe directly connected by being secured to pin 120. Such directconnections between links 110 a, 110 b may strengthen and improve thedurability of track joint assembly 155 by reducing its susceptibility tovibrations and impacts.

Track joint assembly 155 may be configured to facilitate rotation ofbushing 157 relative to pin 120 even when pin 120 is solid (and thuscapable of being manufactured without using costly machining, drilling,or casting processes). In particular, the rotation may be facilitated bycoating one or both of bushing 157 and pin 120 with diamond like carbonor electroless nickel, or by carburizing, nitriding, or polishing one orboth of bushing 157 and pin 120 to reduce friction between bushing 157and pin 120. Alternatively or additionally, the rotation may befacilitated by situating a lubricating fluid between bushing 157 and pin120. Specifically, the lubricating fluid may be added through openings180 a, 180 b in links 110 a, 110 b, and may be contained in lubricatingfluid cavity 190. Since pin 120 is solid, rather than extending into aninterior cavity of pin 120, lubricating fluid cavity 190 may extend intoand be at least partially defined by one or more recesses in innersurface 200 of bushing 157 or outer surface 210 of pin 120.Alternatively or additionally, lubricating fluid cavity 190 may extendinto and be at least partially defined by thrust rings 220 a, 220 b.

Track joint assembly 155 may be configured to minimize the total amountof material required to manufacture links 110 a, 110 b. Suchminimization may be achieved by reducing the number of componentsdisposed in bushing bores 160 a, 160 b of links 110 a, 110 b. Forexample, no collar or seal insert needs to be positioned between bushingbore 160 a and bushing 157, because the material of sealing portion 485of link 110 a may resist wear and corrosion resulting from sealingportion 485's contact with seal assembly 240 a. Thus, inwardly offsetends 140 a of links 110 a may be secured directly to bushing 157,minimizing the number of components disposed in bushing bore 160 a andthus the size of bushing bore 160 a and link 110 a. For example, thediameter of central portion 350 a of bushing bore 160 a may be less than1.49 times the diameter of pin bore 170 a. Additionally, the diameter ofcentral portion 350 a of bushing bore 160 a may be less than 0.87 timesthe outer diameter of outer bushing 250.

Track joint assemblies 155, 155′ and 155″ may be optimized for specificapplications but include many interchangeable parts to minimizemanufacturing costs. For example, track joint assembly 155 may beoptimized for high impact applications in which drive sprockets quicklywear down bushings connecting links 110 a, 110 b, while track jointassemblies 155′ and 155″ may be optimized for low impact applications inwhich bushing wear is not a major concern. As discussed above, however,such optimizations only affect a few parts of track joint assemblies155, 155′, and 155″. Thus, virtually all of the parts of track jointassemblies 155, 155′, and 155″ are interchangeable.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed track jointassemblies. Other embodiments will be apparent to those skilled in theart from consideration of the specification and practice of thedisclosed track joint assemblies. It is intended that the specificationand examples be considered as exemplary only, with a true scope beingindicated by the following claims and their equivalents.

What is claimed is:
 1. A thrust ring comprising: a body including acylindrical outer surface, a cylindrical inner surface, defining acentral axis, an axial direction, a circumferential direction, a firstaxial end, a second axial end, and at least one recess on the firstaxial end, and at least one protrusion extending from the cylindricalinner surface toward the central axis.
 2. The thrust ring of claim 1further comprising a plurality of protrusions extending from thecylindrical inner surface toward the central axis and at least onerecess on the second axial end.
 3. The thrust ring of claim 2 theplurality of protrusions includes three protrusions and the at least onerecess on the first axial end includes two recesses on the first axialend that are disposed diametrically opposite of each other on the firstaxial end.
 4. The thrust ring of claim 3, wherein the at least onerecess on the second axial end includes two recesses that are disposeddiametrically opposite each other on the second axial end, and the tworecesses on the second axial end are out of phase circumferentially withthe two recesses on the first axial end by ninety degrees.
 5. The thrustring of claim 3 wherein the three protrusions are spacedcircumferentially from each other evenly.
 6. The thrust ring of claim 3wherein the three protrusions include a rectangular cross-section andare offset axially from the axial center of the body of the thrust ring.7. A track joint assembly comprising: a first link defining a pin bore,a lubricating fluid cavity bore in communication with the pin bore, andan opening extending from the exterior of the link to the lubricatingfluid cavity; and a thrust ring disposed in the lubricating fluidcavity, the thrust ring comprising a body including a cylindrical outersurface, a cylindrical inner surface, defining a central axis, an axialdirection, a circumferential direction, a first axial end, a secondaxial end, and at least one recess on the second axial end positionedadjacent the opening of the link being in fluid communication therewith,and at least one protrusion extending from the cylindrical inner surfacetoward the central axis.
 8. The track joint assembly of claim 7 furthercomprising a plurality of protrusions extending from the cylindricalinner surface toward the central axis and at least one recess on thefirst axial end.
 9. The track joint assembly of claim 8 wherein theplurality of protrusions includes three protrusions and the at least onerecess on the first axial end includes two recesses on the first axialend that are disposed diametrically opposite of each other on the firstaxial end.
 10. The track joint assembly of claim 7 wherein the openingextends axially and is disposed radially above the pin bore.
 11. Thetrack joint assembly of claim 9 wherein the at least one recess on thesecond axial end includes two recesses that are disposed diametricallyopposite each other on the second axial end, and the two recesses on thesecond axial end are out of phase circumferentially with the tworecesses on the first axial end by ninety degrees.
 12. The track jointassembly of claim 11 wherein the three protrusions are spacedcircumferentially from each other evenly and are offset axially towardthe second axial end.
 13. The track joint assembly of claim 7 furthercomprising a seal assembly positioned radially outward of the thrustring.
 14. The track joint assembly of claim 13 wherein the first link isan outer link and further comprising a second link that is an inner linkdisposed axially next to the first link, the second link defining abushing bore.
 15. The track joint assembly of claim 14 furthercomprising a bushing disposed in the bushing bore axially adjacent thethrust ring.
 16. The track joint assembly of claim 15 wherein thecylindrical outer surface of the thrust ring defines an outer diameterof the cylindrical outer surface, the bushing defines an axial endportion defining an outer diameter of the axial end portion of thebushing and the ratio of the outer diameter of the cylindrical outersurface of the thrust ring to the outer diameter of the axial endportion of the bushing is greater than 1.0.
 17. The track joint assemblyof claim 16 wherein the ratio ranges from 1.1 to 2.0.
 18. The trackjoint assembly of claim 17 wherein the ratio is 1.16.
 19. The trackjoint assembly of claim 16 wherein the seal assembly contacts the secondlink, forming a seal-link interface, the seal-link interface defining anouter diameter of the seal-link interface, and a ratio of the outerdiameter of the seal-link interface to the outer diameter of the axialend portion of the bushing ranges from 1.05 to 2.5.
 20. The track jointassembly of claim 19 wherein ratio of the outer diameter of theseal-link interface to the outer diameter of the axial end portion ofthe bushing is 1.20.